The present invention relates to a vehicle braking system and a master cylinder.
As a technology for shortening a stroke of a brake pedal so as to obtain a good pedal feel, a master cylinder including a large-diameter pressurized chamber and a small-diameter pressure chamber is known, for example. The master cylinder performs so-called fast fill for supplying a large volume of brake fluid from the large-diameter pressurized chamber to the small-diameter pressure chamber during an initial stage of the stroke so as to compensate for an ineffective fluid amount during the initial stage of the stroke. Thereafter, a pressure-reducing valve is opened at a predetermined hydraulic pressure to reduce a hydraulic pressure in the large-diameter pressurized chamber. As a result, a desired braking force is obtained while the stroke of the brake pedal during the initial stage of the stroke is shortened. An example of the master cylinder as described above is described in Japanese Patent Application Publication No. 2002-321609.